(a) Field of the Invention
The present invention relates to a method of determining blocking in a ring network and, more particularly, to a method and apparatus of determining logical blocking set to prevent an infinite loop of Ethernet frames transferred in an Ethernet ring network.
(b) Description of the Related Art
In an Ethernet ring network, two ports of respective nodes are connected to ports of adjacent nodes to constitute a ring overall, and a certain link in the Ethernet ring network is blocked to prevent a transmission of Ethernet frames from forming an infinite loop, thus logically forbidding a ring formation. To this end, a predetermined particular port among several ports of the Ethernet ring network is blocked, and here, the blocked link is merely logically determined and a physical link exists, so the logical blocking is lifted, traffic can be immediately transferred.
When logical blocking is set in the Ethernet ring network, an Ethernet frame cannot be transmitted to the blocked link, so transmission paths of numerous service flows that may exist in the Ethernet ring network are determined by the set logical blocking irrespective of an optimum path. For example, in case in which the Ethernet ring network includes N number of links and N number of nodes and a traffic request amount of the service flows transmitted and received between respective nodes is determined by N×N matrix, the number of cases that one link is logically blocked by the logical blocking may be N. Also, since transmission paths between the respective nodes are changed due to each logical blocking, a total amount of traffic transferred through N number of links in the Ethernet ring network is changed. Thus, according to circumstances, traffic is concentrated on at least one link in the Ethernet ring network, causing traffic overload.
In the Ethernet ring network, as for a ring capacity, an equal bandwidth is provided in both directions for all the links, so the ring capacity is determined based on a link that transfers the largest amount of traffic. If a certain link exceeds the ring capacity due to arbitrarily set logical blocking in the Ethernet ring network, the ring capacity should be over-provisioned in order to prevent a loss of an Ethernet frame. As a result, in the network operator position, in order to prevent an unnecessary network over-provisioning for the Ethernet ring network, a scheme for minimizing the ring capacity of the Ethernet ring network by selecting an optimal logical blocking position may be required.
Also, unlike minimization of the ring capacity of the Ethernet ring network, a traffic overload due to logical blocking arbitrarily set in the Ethernet ring network may be prevented through logical blocking that minimizes a traffic request amount of every service flow existing in the Ethernet ring network, so a scheme for logical blocking that minimizes a traffic request amount of every service flow may also be required.